Introduction to SIGADs

SIGADs are used for intercept facilities operated by the signals intelligence agencies of the United States, the United Kingdom, Canada, Australia and New Zealand, as these five countries have a close relationship for collecting and sharing signals intelligence under the so-called UKUSA-agreement.

Since World War II several thousand SIGADs have been assigned. A screenshot of the NSA's BOUNDLESSINFORMANT tool showed that in March 2013 there were 504 active SIGADs, which means that in that month NSA collected data from 504 intercept facilities. This number probably includes many subsets and maybe a several dozen are really significant sources.

A typical SIGAD looks like USN-855

The first two letters indicate the country and can be US for the United States, UK for the United Kingdom, CA for Canada, AU for Australia and NZ for New Zealand.

Then comes one letter indicating what sort of staff runs the station, which can be M for Army, N for Navy, A for Air Force, J for Joint services (mainly military), F for Joint services (mainly civilian), D for Detachment or C for Civilian staff.

After a hyphen follows a unique number which identifies the particular facility.

An additional alphabetic character is added to denote a sub-designator for a subset of the primary collection unit, like a detachment. Lastly, a numeric character can be added to provide for a sub-sub-designator.

An example of a SIGAD with a sub-sub-designator is US-987LA

These sub-designators can also be represented by an X for an alphabetic character and an N for a numeric character.

Down below is a list of all known SIGADs from past and present and from all five UKUSA-countries. Sorting the unique numbers in groups of hundreds, revealed that they are apparently assigned according to this scheme:

CFS Alert should also have a SIGAD, and there are likely to be additional SIGADs associated with Internet exchange points, the intercept facilities located in some Canadian embassies, and perhaps fibre optic cable taps, but those designators are not currently public knowledge.

Top Level Telecommunications also has a fascinating discussion of the SIGADs associated with the NSA's PRISM and BLARNEY programs.

As far as I can judge, these two posts provide an excellent distillation and analysis of what is publicly known about the SIGAD designators. (The other posts on the blog also make very interesting reading.)

However, the suggestion that the AFP numbers associated with some U.S. military space programs are the SIGADs for those systems is, I believe, not correct. As Dwayne A. Day explains here, AFP numbers were used for a wide variety of space programs, including SIGINT satellites, but also including communications satellites, meteorological satellites, R&D satellites, IR/early warning satellites, and photo reconnaissance satellites. Furthermore, unlike SIGADs, AFP numbers were used for public references to those various programs.